Use the effect of "Wind-Up Soldier" to have it gain 400 ATK ,then use this card to double its ATK to 4400. During the End Phase, it returns to the hand, so this process can be repeated again on your next turn or use "Soldier" for a Rank 5 Xyz Summon.
Xyz Summon with the affected monster before the End Phase if used on your turn.
When your opponent attacks your "Wind-Up Rabbit", use this in the Damage Step. Then, during your End Phase, banish "Rabbit" with its effect instead of returning it to your hand.